Several are capable of efficient emission of laser and fluorescent light in the ultraviolet portion of the spectrum contain chemically reactive halogen species such as fluorine or chlorine. High-frequency excitation of these halogen-containing gas is desirable since it does not require the use of chemically-reactive metal electrodes inside the discharge tube. However, it is necessary to fabricate the discharge tube itself from halogen-compatible materials in order to achieve long operating lifetimes from these devices.
Gas discharge tubes in which optically-emitting gases are excited by high frequency (10 MHz to 10 GHz) electromagnetic fields are used in many types of lasers and lamps. Christensen (U.S. Pat. Nos. 4,631,732; 4,789,909; 4,796,271) and Harris and Young (U.S. Pat. No. 4,802,183) have disclosed high frequency discharge devices suitable for excitation of rare gas halide excimer laser systems. The disclosures of these patents are incorporated herein by reference. Kumagai and Obara (Applied Physics Letters, 54,2619 (1989)) have described high efficiency lamps utilizing rare gas/halogen mixtures. In this prior art the gas mixtures were contained in a dielectric discharge tube fabricated from borosilicate glass and fused quartz materials or aluminum oxide. Although glass and fused quartz materials can be formed and shaped by conventional glassworking techniques, they are etched and corroded by the halogen discharge plasmas, particularly those containing fluorine. Aluminum oxide is more chemically resistant to the halogen discharge plasma, but it is difficult to form and shape due to its extreme hardness and high melting point.